Communicable Diseases Overview

Communicable Diseases

• A communicable disease spreads from person to person or animal to human.
• Four major pathogen types: bacteria, viruses, fungi, and protists.
• Bacteria are small cells producing toxins that harm cells. Examples: Salmonella, Gonorrhea.
• Viruses are non-cellular, using the host's cells for replication. Antibiotics are ineffective. Examples: Measles, HIV.
• Fungi can be single-celled or multicellular, causing diseases. Example: Rose Black Spot (causes black spots on plant leaves, reducing photosynthesis).
• Protists are often single-celled eukaryotes. Many are parasites, like the malaria parasite transferred by vectors (e.g., mosquitoes).

Preventing the Spread of Disease

• Hygiene: Washing hands prevents disease transmission (e.g., before food prep, after sneezing).
• Vector control: Limiting insect vectors (e.g., mosquitoes) controls diseases like malaria (e.g., using insecticides, destroying breeding grounds).
• Isolation: Isolating infected individuals prevents further spread.
• Vaccination: Vaccination creates herd immunity, protecting unvaccinated individuals, when enough are vaccinated.

The Body's Defenses Against Disease

• First Line of Defense: Physical barriers (skin, enzymes, hairs, stomach acid, mucus) prevent pathogen entry.
• Second Line of Defense: Phagocytes are white blood cells that engulf and destroy pathogens. Antibodies bind to pathogens, clumping them for easier phagocytosis.
• Third Line of Defense: Lymphocytes (white blood cells) recognize specific pathogens (antigens). A subsequent exposure triggers a faster antibody-based response.

Vaccination

• Vaccination introduces a dead or inactive pathogen, triggering an immune response.
• This is harmless but stimulates antibody production and memory cell formation.
• Phagocytes engulf the pathogen, allowing lymphocytes to remember the antigen and store antibodies.
• If the live pathogen enters the body, the immune system swiftly fights the disease.

Drug Development

• Drug development is a multi-stage process for safety and effectiveness assessment.
• Stage 1: Computer models assess drug potential.
• Stage 2: Testing on cells or tissues to evaluate effects.
• Stage 3: Animal studies assess effects on whole organisms.
• Stage 4: Human clinical trials using placebos and double-blind designs to determine efficacy.
  • Placebo: A harmless, fake drug to compare effects with the real drug.
  • Double-Blind Trial: Neither patient nor researcher knows who received the real or placebo treatment. This minimizes bias.
• Efficacy: Drug effectiveness in treating the disease.
• Dosage: The amount of drug necessary for the desired effect.
• Toxicity: Potential side effects of the drug.